Bloomberg ran an article last week titled, “Climate Change Will Cut Corn Yields by a Quarter by 2030, NASA Says“. The article was circulating around the trade and catching a lot of attention, so I thought we should take a deeper look.
Whatever side of the aisle you sit on in the climate change debate, it is tough to deny that weather patterns in most U.S. growing regions have witnessed dramatic shifts over the last couple of decades. Weather events, including drought, thunderstorms, and hurricanes have also become more extreme. With these trends expected to continue, the production of corn and wheat-two of the world’s biggest staple crops-will also likely be impacted, according to a new study that included researchers from NASA, as well as the IIASA and the Potsdam Institute for Climate Impact Research (PIK). Using advanced climate and agricultural models, the scientists project that corn yields could decline as much as -24% while wheat yields could increase by about +17% by 2030.
‘We did not expect to see such a fundamental shift, as compared to crop yield projections from the previous generation of climate and crop models conducted in 2014,’ said the study’s lead author Jonas Jägermeyr, a crop modeler and climate scientist at NASA’s Goddard Institute, in a statement. Jägermeyrwas especially concerned at the projected decline in corn, adding, “a -20% decrease from current production levels could have severe implications worldwide.” The study projects corn growers in North and Central America, West Africa, central Asia, Brazil, and China will potentially see their maize yields decline in the coming years as average temperatures rise across these breadbasket regions, putting more stress on the plants.
In contrast, wheat, which grows best in temperate climates, may see a broader area where it can be grown as temperatures rise, including the northern United States and southern Canada, the north China plains, central Asia, southern Australia, and East Africa. However, these gains may level off by mid-century. The researchers found that the change in yields is due to projected increases in temperature, shifts in rainfall patterns, and elevated atmospheric carbon dioxide concentrations from greenhouse gases. Soybeans and rice are also set to be negatively impacted, though the models created by the researchers give varying levels of impact, ranging from a decline of -2% to as much as -21%.
“When we look at future climate change, it’s not the same as the current hot years that we experience,” said Alex Ruane, a Goddard Institute scientist and coauthor of the study. He also coordinates and leads the climate team for the Agricultural Model Intercomparison and Improvement Project (AgMIP), an international partnership coordinated by Columbia University. Ruane notes that if you look at a recently hot year experienced in any one location, it would likely have been a heat wave that would have raised the overall temperature. “Climate change is different. Climate change is every day, a little bit more and more. When those heat waves come [in the future], they’re just a little bit more intense or extreme, and that has a different physiological impact on plants.”
To arrive at their projections, the research team used two sets of models. Then the research team used the climate model simulations as inputs for 12 state-of-the-art global crop models that are part of AgMIP. The crop models simulate on a large scale how crops grow and respond to environmental conditions such as temperature, rainfall and atmospheric carbon dioxide, as provided by the climate models. Each crop’s behavior is based on its real life biological responses studied in indoor and outdoor lab experiments. As Ruane explains, “What we’re doing is driving crop simulations that are effectively growing virtual crops day by day, powered by a supercomputer, and then looking at the year-by-year and decade-by-decade change in each location of the world.” In the end, the team created about 240 global climate-crop model simulations for each crop.
Temperature is not the only factor the models consider when simulating future crop yields. Higher levels of carbon dioxide in the atmosphere have a positive effect on photosynthesis and water retention. This increases crop yields, but often at a cost to the nutritional values of crops. This effect happens more so for wheat than maize. Rising global temperatures also are linked with changes in rainfall patterns, and the frequency and duration of heat waves and droughts, which can affect crop health and productivity. Higher temperatures also affect the length of growing seasons, and accelerate crop maturity.
“We care about climate change not because of degrees Celsius or parts per million CO2, but because those in turn affect all sectors and our lives,” said Ruane, referring to not only the large-scale agricultural sector and economy, but also the everyday changes that will happen as communities respond to climate change. The study focused only on climate impacts. The models do not address economic incentives, changing farming practices, or adaptations such as breeding hardier crop varieties, although that is an area of active research. The research team plans to look at these angles in followup work, since they will also determine the fate of agricultural yields in the future as people respond to climate-driven changes. You can learn more HERE. (Sources: NASA, Nature, Columbia.edu)